Hydrocarbon and carbonaceous feedstock can be converted into H2 and CO synthesis gas mixtures with varying ratios of H2 to CO. Feedstock may include coals, natural gas, oil fractions, bitumen and tar-like refinery wastes, pet-coke and various forms of biomass. The synthesis gas mixtures can be converted into valuable hydrocarbons and chemicals using catalytic processes. The synthesis gas can also be converted to H2 by reaction of the CO component with steam over a catalyst followed by CO2 removal to produce a fuel gas which can be burned in a gas turbine combined cycle power production system resulting in power production with CO2 capture. The conversion of synthesis gas to valuable hydrocarbon and chemical products generally requires a large additional amount of power to be provided to the process and this can be produced from a gas turbine system. The conversion of these fuels to synthesis generally requires large volumes of oxygen which is typically used in a partial oxidation of the feedstock. This oxygen can be produced in a high temperature oxygen ion transport membrane system which separates oxygen from a high pressure high temperature air stream by diffusion from a region of high oxygen partial pressure to low oxygen partial pressure. The source of the high pressure high temperature air stream can be the compressed air stream produced in a gas turbine. It is the objective of this invention to disclose a method of integrating an oxygen ion transport membrane with a gas turbine using a hydrogen rich carbon depleted fuel gas to produce simultaneously power and pure oxygen with high efficiency. It is apparent that the integration of ITM O2 production modules with existing unmodified gas turbines requires an external air compressor supplying part or all of the air flow required for O2 production.
It is the objective of this invention to propose a system which will allow all the fuel gas combustion heat used for air preheating to be recovered at the gas turbine combustion heat input level so that recovered heat can produce electrical power at 55% to 60% net efficiency.
It is a further objective of this invention that the fuel gas is effectively diluted with a nitrogen rich diluent and supplied at a temperature below 500° C. without loss of efficiency caused by transferring heat to the steam system.
It is a further objective of this invention to ensure that the oxygen content of the diluent stream is reduced to a concentration at the ITM exit which will never give any safety hazard when diluent and H2 or (H2+CO) fuel gas at elevated temperature are mixed.
It is a further objective of this invention that the mixture of H2 or (H2+CO) fuel gas and diluent is within the necessary LHV value for satisfactory combustion in a gas turbine. The range would be for LHV values to be greater than about 120 Btu/scf and that the diluted fuel gas mixture would be at the maximum temperature allowed by the gas turbine vendor.
Previous methods for optimizing the integration of a gas turbine and an Ion Transport Membrane which diffuses pure oxygen from a pressurized heated feed air stream have disadvantages compared to the present invention as described below.